Universal modem for digital video, audio and data communications

ABSTRACT

A universal modem has a software-configurable modulator/demodulator which commodates different modulation formats such as those associated with terrestrial, cable, phone line, satellite and wireless communications to be transmitted and received through a single device in which the modem has reconfigurable logic to accommodate the format of the signals being received or transmitted. Note that the modulator or demodulator can be used separately or the two units can be combined and used for transceivers, with either the same software configuring both the modulator and demodulator, or with different software used for the two units. In the receive mode, the universal modem detects the modulation format of the incoming signal and reconfigures the logic of its software-configurable demodulator to output demodulated digital data for further processing. In the transmit mode, information to be transmitted is provided with the appropriate modulation format by setting a software-configurable modulator in the universal modem to the particular format. In one embodiment, in the receive mode the incoming signal is A-D converted, with a host processor utilized to detect the type of modulation associated with the incoming signal and through a configuration controller configures a random access memory which is coupled to the software-configurable demodulator. In advanced television applications, the demodulated signal is passed through an equalizer, a Trellis Decoder and Reed-Solomon Decoder to provide an appropriate filtered and level-adjusted digital signal that is coupled to the next processing stage.

FIELD OF INVENTION

This invention relates to modulators and demodulators and, moreparticularly, to a universal modem which is configurable to process oneof a number of modulation formats.

BACKGROUND OF INVENTION

In recent years due to the rapid development of multimedia, digital,audio and video communication applications, there is a necessity forefficient and reliable signal modulation and demodulation techniques toaccommodate different modulation formats chosen based on the media overwhich the signals are to be transmitted.

For instance, with respect to high definition television, and in factother types of advanced television transmissions, program material invideo, data or audio form is formatted by a channel encoder so as to betransmittable by Vestigial Side Band modulation or VSB which is typicalfor over-the-air television transmissions. On the other hand, QuadratureAmplitude Modulation or QAM is typically used for cable transmission,whereas Quadrature Phase Shift Keying or QPSK is generally used insatellite communication. Finally, discrete multitone or DMT techniquesare typically used for telephone landline signalling such as withAsymmetric Digital Subscriber Lines or ADSL.

It will be appreciated that when a video source at the transmit side isencoded through a source coding unit, the source coding unit is set upto code the video source material in one of the four above-mentionedmodulation formats. Likewise, on the receive side, in order for areceiver to decode all of the above-mentioned formats discrete VLSIchips or detectors can be provided in parallel, with the outputs goingto source decoding. It will be readily apparent that because there ispresently no universal modulation format, receivers destined to beutilized not only for over-the-air transmissions, but also for cablemust at least have the capability of decoding the appropriate modulationformat. While it is possible to use a parallel brute force approach bymerely providing the receive side with a series of demodulators eachconfigured to demodulate a particular format, this approach is costlyand error-prone.

As to the parallel approach mentioned above, it is possible to design amodem in which the input signal is fed from the RF-IF stage of thereceiver in parallel to each of four demodulators, with the output ofeach demodulator being switched to source decoding depending on themodulation format of the received signal. Modulation format can bedetermined in some instances by the channel to which the receiver istuned, although this can vary from country to country.

For instance, in the United States, for VHF channels 1-13 and UHFchannels, VSB modulation is used, with the VSB demodulator switched tosource decoding. For the cable channels, generally over Channel 68, QAMmodulation is used, with the output of the QAM demodulator switched tosource decoding. For satellite channels, QPSK modulation is used, withthe QPSK demodulator switched to source decoding, whereas for telephoneline usage, assuming a channel indicating landline transmission, it isthe DMT output of a demodulator which is switched to source decoding.

This duplication of demodulators aside from being four times the expenseof a single demodulator, also has the following problems: First andforemost, it will be appreciated that in order to switch the outputs ofthe various demodulators to source decoding, the output of thedemodulators must have a high impedance to damp switching transients andlike anomalies. Secondly, care must taken to eliminate cross modulationbetween the different demodulators.

It will thus be appreciated that any parallel processing solution to theproblem of multiple modulation formats generally resolves itself into aquestion of the cost associated with duplicating demodulators andtechnical complexity which is indeed a factor in mass marketedmultimedia receivers for which such demodulator cost duplication andcomplexity is unacceptable.

On the transmit side, for multimedia transmissions requiring differentmodulation formats, duplicating modulators are likewise expensive anderror-prone in much the same way as described above with respect todemodulators. Also, with specialty services such as data to be providedon different channels, oftentimes the modulation format is differentfrom that of the main transmission. To provide such additional servicesordinarily would require separate modulators having the expected costimpact.

SUMMARY OF THE INVENTION

Rather than multiplying the number of demodulators and modulators to beable to demodulate the differing modulation formats and to provide fordiffering modulation formats, in the subject invention, a universalmodem is provided which is based on reconfigurable logic for itsdemodulator as well as its modulator. In one embodiment, a host computerat the receive side detects the modulation type and reconfigures thedemodulator in universal modem to demodulate the format of the incomingsignal.

In this embodiment in the receive mode, a host computer detects themodulation type of the incoming signal by detecting the channel to whichthe receiver is tuned and setting the demodulator to the expectedformat. Thus if the receiver is tuned to a given channel, then theuniversal modem is reconfigured to the expected format of signals onthat channel. This is done on an a priori basis since different groupsof channels have different standardized formats.

Alternatively, the host computer can detect the format of the incomingsignal by detecting a flag in the header of the incoming data streamindicating modulation type, assuming one is loaded into the header atthe transmit side. This type of demodulation selection does not requirea priori knowledge of the correlation of channel with modulation type.As will be appreciated, in different countries different channels areassigned to different types of service which makes this alternativemethod of ascertaining the channel modulation type attractive. Theabove, of course, requires that a modulation type flag be generated inthe source coding at the transmit side.

In one example of the use of the universal modem in the ATV or advancedtelevision transmission mode, assume that video data is to betransmitted in the MPEG format, where MPEG stands for Motion PictureExpert Group and where one utilizes the MPEG-2 format currently invogue. Video information is source coded in MPEG in which 188 bytes ofinformation are transmitted as a packet. Channel coding which definesthe modulation format is imposed on top of the source coding to provideerror correction which adds typically 20 more bytes of information tothe data stream.

After the video information has been source coded and channel coded bythe software-configurable modulator for a given format, it is ready fortransmission. Note that prior to the transmission of the data, a header,e.g. a 3-bit header word: 000=VSB, 001=QAM, 010=QPSK, 011=DMT etc., canbe inserted into the channel coding so as to provide an indication ofthe modulation type.

While the above has been described in terms of standardized formats forterrestrial, cable, satellite or telephone communications, the universalmodem is also applicable to such diverse areas as cellular, PCS andother wireless services to provide automatic reconfiguring of atransceiver to permit its use across different formats. This isespecially useful with cellular phone formats CDPD, CDMA, TDMA, FDMA andGSM referring respectively to cellular digital packet data, codedivision multiplexing, time-division multiplexing, frequency-divisionmultiplexing, and the global mobile system type of modulation. While acellular phone may be provided in one community for use with CDMA, whenthe phone roams to an area where TDMA transmissions are utilized, auniversal modem within the phone can detect the change and reconfigurethe demodulator side of the modem. Likewise, since the cellular systemis a full duplex system, the universal modem can be reconfigured in thetransmit mode to appropriately format the cellular transmission. It willof course be appreciated that the universal modem can be used with anytype of RF transceiver roaming from one area to another where differentformats are used, regardless of the type of service that is authorized.

Further, the universal modem is applicable to any kind of digitalmodulation method. For instance, it can be applied to digitalterrestrial broadcasting utilizing the OFDM or Orthogonal FrequencyDivision Multiplexing method scheduled for use in Europe, Japan and/orother countries.

In one embodiment, the demodulation section of the modem, involves ananalog-to-digital converter to provide a digital bit stream to ademodulator which is software-reconfigured in accordance with the outputof a configuration RAM. In this embodiment, circuit blocks, elements ormodules within the demodulator are linked up to provide a particulartype of carrier recovery in accordance with the output of theconfiguration RAM. In another embodiment, the demodulator is layered,with each layer containing a different carrier recovery circuit. Theconfiguration RAM can call for a given type of demodulation merely byactivating one of the layers. This means that in any event, theconfiguration of the demodulator can be fixed by providing it withblocks, elements or modules that are connected in a particular way onthe fly in response to the output of a configuration RAM under thecontrol of a configuration controller. In a further embodiment, thesoftware-configurable demodulator can be implemented in software using ageneral purpose microprocessor. Note that the above softwarereconfiguration techniques utilized for the demodulator can likewise beused for a software-configurable modulator.

For over-the-air and cable signals requiring equalization, the output ofthe configuration RAM may also be utilized to reconfigure an equalizercoupled to the output of the demodulator. Alternatively, when nofollow-on signal processing is required, the only element that is to bereconfigured is the demodulator. It will be noted that equalizers are ingeneral used to correct intersymbol interference, whereas in televisionapplications, equalizers are used to cancel ghost images.

As to setting of the universal modem for modulation type or format asmentioned before, flags can be used on the transmission which aredetected at the receive side. Alternatively, the channel to which thereceiver is tuned can be detected. Moreover, a smart card or othersimilar device can be used to set the modulation type or format at thereceive side. An additional way of detecting modulation type is todemodulate an incoming data stream using all possible formats, detectingthe error and setting the demodulator to the modulation type having thelowest error.

In summary, a universal modem has a software-configurablemodulator/demodulator which accommodates different modulation formatssuch as those associated with terrestrial, cable, phone line, satelliteand wireless communications to be transmitted and received through asingle device in which the modem has reconfigurable logic to accommodatethe format of the signals being received or transmitted. Note that themodulator or demodulator can be used separately or the two units can becombined and used for transceivers, with either the same softwareconfiguring both the modulator and demodulator, or with differentsoftware used for the two units. In the receive mode, the universalmodem detects the modulation format of the incoming signal andreconfigures the logic of its software-configurable demodulator tooutput demodulated digital data for further processing. In the transmitmode, information to be transmitted is provided with the appropriatemodulation format by setting a software-configurable modulator in theuniversal modem to the particular format. In one embodiment, in thereceive mode the incoming signal is A-D converted, with a host processorutilized to detect the type of modulation associated with the incomingsignal and through a configuration controller configures a random accessmemory which is coupled to the software-configurable demodulator. Inadvanced television applications, the demodulated signal is passedthrough an equalizer, a Trellis Decoder and Reed-Solomon Decoder toprovide an appropriate filtered and level-adjusted digital signal thatis coupled to the next processing stage.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of the subject invention will be betterunderstood taken in conjunction with the Detailed Description inconjunction with the Drawings of which:

FIG. 1 is a block diagram of the transmit side of a modem indicating theutilization of multiple discrete modulators;

FIG. 2 is a block diagram of the receive side of the modem of FIG. 1indicating the utilization of multiple demodulators coupled to sourcedecoding, in which the demodulator corresponding to the format of theinput signal is switched to source decoding;

FIG. 3 is a block diagram of the receive side of the subject universalmodem indicating multiple inputs of differing formats, with theuniversal modem detecting which format the incoming signal possesses andthen internally reconfiguring itself;

FIG. 4 is a block diagram of the transmit side for the subject universalmodem in which the universal modem is utilized to encode signals inaccordance with the intended modulation mode of the signal;

FIG. 5A is a block diagram of one embodiment of the receive side of thesubject universal modem indicating the utilization of a configurationcontroller, configuration RAM and a configurable demodulator incombination with an equalizer, a Trellis Decoder, and an R-S Decoder.

FIG. 5B is a block diagram of one embodiment of the transmit side of thesubject universal modem indicating the use of a configuration controllercoupled to a configuration RAM in which the modulation format is set inaccordance with the desired transmit channel.

FIG. 6 is a diagrammatic representation of the configurable demodulatorof FIG. 5A;

FIG. 7 is a schematic diagram of a typical squaring/phase locked loopcarrier recovery system to which the demodulator of FIG. 5A can beconfigured;

FIG. 8 is a schematic diagram of a typical Costas loop carrier recoverysystem to which the demodulator of FIG. 5A can be configured;

FIG. 9 is an algorithm for the demodulation of QPSK/QAM which can bebroken into elements and used for the demodulator of FIG. 5A;

FIG. 10 is a block diagram of a smart card system for setting thesoftware configurable logic unit of the demodulator of FIG. 3; and,

FIG. 11 is a block diagram of a system for detecting modulation typebased on an error signal which is the result of demodulating allpossible modulation types.

DETAILED DESCRIPTION

As mentioned above, the rapid deployment of multimedia, digital, audioand visual communication applications calls for efficient and reliablesignal modulation and demodulation methods. As illustrated in FIGS. 1and 2, signals transmitted via different media are modulated anddemodulated differently. For instance, on the transmit side, sourcecoding 10 takes video content from a video source 12 and encodes it intobit streams, whereupon the output of source coding unit 10 is applied inparallel to modulators 14, 16, 18 and 20 respectively VSB, QAM, QPSK andDMT modulators. The formats for VSB, QAM, and QPSK modulation techniquesare described in K. Blair Benson, Television Engineering Handbook,Revised Edition, McGraw-Hill, 1992. The format for DMT is described inBellcore, Framework Generic Requirements for Asymmetric DigitalSubscriber Lines, FA-NWT-001397, No. 1, December, 1992 and in "Notice tothe Industry: ADSL Equipment", Bellcore Digest of Technical Information,June, 1993, p. 40.

The decision as to which modulation technique is to be utilized in, forinstance, terrestrial over-the-air signalling or cable signalling, isfounded in both political and technical considerations. Historically,VSB was the format originally used to transmit over-the-air videosignals. In the early days of television, Vestigial Side Band Modulationwas deemed to be the most efficient modulation method, whereas, withrespect to cable, Quadrature Amplitude Modulation gave superiorperformance. Regardless of the modulation format, there exist numerousmodulation schemes which must be accommodated by a universal modem.

On the receive side, as illustrated in FIG. 2, in a parallel processingscheme an incoming signal is down converted by RF-IF converters, hereillustrated by reference characters 22, 24, 26, and 28, coupled torespective demodulators 30, 32, 34 and 36. For ATV receivers, the VSBand QAM modulators are available from major television manufacturers, aswell as being under development in a joint development program betweenMitsubishi Electronics America and Lucent Technologies, Inc. QPSKdemodulators are available from Philips Semiconductors, Part No.TDA8040T, among others. DMT-based ADSL equipment is described in "Noticeto the Industry: ADSL Equipment", Bellcore Digest of TechnicalInformation, June, 1993, p. 40. As mentioned hereinbefore, the outputsof these demodulators are switched to a source decoding unit 38, such asthe Mitsubishi MH-1000D.

The problem associated with multiple formats is that the number ofmodulation schemes now contemplated for use and in the future, aremultiplying. Presently, there is no way of ascertaining which modulationschemes will dominate. It is therefore encumbant on the manufacturer oftransceivers to be able to accommodate as many modulation schemes aspossible with a minimum amount of hardware.

Referring now to FIG. 3 in the subject system on the receive side, auniversal modem 40 which is software-reconfigurable has as an inputeither a terrestrial signal 42, a cable signal 44, a satellite signal 46or a landline signal 48, each with its own unique modulation format.Here the signals are coupled to respective RF-IF converters 50, 52, 54and 56. The output of the universal modulator is in turn coupled toconventional source decoding 58.

As will be discussed in FIG. 5A, the universal modem is reconfigurabledepending either on the channel to which the receiver is tuned, or ondetection of format flags. The universal modem is thus provided withconfiguration control signals derived either through a priori knowledgeof the modulation type associated with a channel or actual detection offormat flags.

Referring now to FIG. 4, on the transmit side of the universal modem,source coding 60 is coupled to universal modem 40 which in turnconfigures the modulator in the modem to output bit streams having therequired modulation format dependent on the media, namely, terrestrial42, cable 44, satellite 46 and landline 48. Here, the modulator issoftware-configurable, which eliminates the requirement for a pluralityof modulators. It will thus be appreciated that modem 40 reformats theprogram material or video source from source coding 60 so as to put thematerial into a modulation format which is compatible with theparticular medium over which the information is to be transmitted. Ingeneral, modem 40 performs function of channel coding, with the channeldictating the particular modulation format. As can be seen, the outputof modem 40 is provided to that IF-RF converter 62, 64, 66 and 68required for the associated media.

There are several advantages of having a software reconfigurablemodulator:

First, when used in multimedia applications, the role of the universalmodem is of a network interface module. In addition to having thecapability of receiving from multiple transmission media applyingdifferent modulations, it allows the user to send signals, such asrequest for data or audio/video services, via different return channelshaving different modulation platforms. This not only increases theflexibility and mobility of the device, it also benefits theoptimization of return channel bandwidth and utilization efficiency.

Secondly, when used in broadcast services, the universal modem providesa low cost modulation platform which can be changed under softwarecontrol from one modulation format to another. This benefits regionalstations which typically have a small number of channels to provideservice with, but obtain their programs from more than one serviceprovider and network involving multiple modulation types.

Thirdly, the advantages for PCS referred to hereinabove include theability to instantly switch from one format to another when roaming,depending on the area the cell phone is in, thus to switch from TDMA toCDMA and vice versa as an example. Note that the CDMA system isdescribed in U.S. Pat. No. 5,103,459 entitled SYSTEM AND METHOD FORGENERATING SIGNAL WAVE FORMS IN A CDMA CELLULAR TELEPHONE SYSTEM.

Referring now to FIG. 5A, in one embodiment, the receive side of theuniversal modem includes an input 70 from tuner 71 which is coupled to afront end 72 whose primary purpose is level adjustment, amplificationand filtering of the incoming signals from the tuner. Note that thetuner is set to a given channel by channel select 73. The output offront end 72 is coupled to A-D converter 82, and thence tosoftware-configurable demodulator 84. Additionally, in one embodiment,the header of the input signal is stripped off and provided to a hostprocessor 74 which determines from flags in the header the modulationformat type. Alternatively, the host processor can determine themodulation format through channel input 76 from the channel select 73.In either event, the output of the host processor specifies themodulation format to a configuration controller 78, the purpose of whichis to select from a configuration RAM 80 the appropriate demodulationmode to be downloaded to demodulator 84.

In one embodiment, demodulator 84 is provided with a an array of gates,arithmetic logic units or ALUs, registers and other circuit blocks,elements or modules which can be connected together to provide a circuitto recover the associated carrier. In a preferred embodiment, at ahigher level, the demodulator is configured in layers, with each layercontaining gates and logic as well as filtering to provide a circuitspecially tailored for carrier recovery of a different modulation formattype. The configuration RAM therefore merely selects which of the layersis to be activated, thereby, taking advantage of the embedded logic ineach of the layers.

In a VLSI realization of the universal modem, the universal modemhardware is realized in a VLSI chip, using the logic implemented withDRAM technology and hardware-software codesign. In one embodiment, thecommunication between the configuration control and the host processoris provided by an I² C bus. The configuration RAM can be implementedwith either DRAM- or SDRAM technology, with the latter ensuring fasterexecution, which is desirable if the amount of data to be stored is verylarge.

Put another way, the building blocks, elements or modules within thedemodulator are quite similar across the entire spectrum of modulationformats. This being the case, these blocks, elements or modules arecapable of being connected together in a different manner for each ofthe modulation types. Thus, the configuration RAM 80 instructsdemodulator 84 as to how it is to be reconfigured for the particularmodulation type.

As mentioned hereinbefore, for over-the-air applications, the output ofdemodulator 84 is coupled to an equalizer 86 which, in one application,is utilized for ghost cancellation or to reject intersymbolinterference. The output of equalizer 86 is coupled to a Trellis Decoder88, the purpose of which is to eliminate errors in the bit level of theincoming signal, whereas a Reed-Solomon Decoder 90 is utilized to removebyte level errors. The output of decoder 90 is coupled to I/O 92 whichforms the output of the demodulation section of the subject universalmodem.

Referring now to FIG. 5B, on the transmit side, the universal modem, inone embodiment, has an input 71 coupled to an I/O stage 73, which is inturn coupled to an R-S encoder 75. This encoder is in turn coupled to aTrellis encoder 77 which is then coupled to a software-configurablemodulator 79. The output of modulator 79 is coupled to adigital-to-analog converter 81 and thence to an UP converter 83 underthe control of a channel select unit 85. The channel assigned to thetransmitted signal is selected and the output of D/A converter 81 isupconverted to the appropriate carrier frequency.

As mentioned before, the modulation type or format is correlatable tothe transmit channel. The software-configurable modulator is set inaccordance with the selected channel by use of a host processor 87 whichreads out channel select 85. Host processor 87 outputs the channel to aconfiguration controller 89 which drives a configuration RAM 91 toconfigure modulator 79 to the appropriate format. Configuration RAM 91also sets Trellis encoder 77 to the appropriate channel.

In this way, the modulation section of the universal modem issoftware-configurable to a predetermined format, in one instance,correlated to the transmit channel. The software-configurable modulatoris then quite flexible.

Referring now to FIG. 6, demodulator 84 typically includes blocks,elements or modules such as arithmetic logic unit 94, a number ofregisters 96, at least one First-In-First-Out or FIFO memory 98,multiplexers 99, one or more finite impulse response filters 100, andone or more infinite impulse response filters 101 as well as numerousgates 102, 104 and 105 which may be NOR gates, AND gates, OR gates orany of the typical logic level devices.

It is the purpose of the demodulator to extract carrier and timinginformation. How this is accomplished is in major part due to theparticular type of finite impulse response filter employed. Thecombination of ALU registers, FIFO's, multiplexers, and gates as well asfinite impulse response and infinite impulse response filters is thatwhich successfully demodulates the signal, with interconnection of thesedevices being under the control of configuration RAM 80 of FIG. 5A.

Referring now to FIG. 7, a typical squaring loop carrier recovery systemis illustrated in which the functions performed by the low pass filterand the voltage control oscillator as well as the divide-by-two circuit,the mixer and the squaring circuit can be replicated in a singlereconfigurable chip so that all of these blocks can be connectedtogether on the fly.

Referring now to FIG. 8, likewise in Costas loop carrier recovery, thephase shifter, low pass filter, VCO, loop filter as well as the mixerelements are available as blocks in the demodulator which, whenconnected as illustrated, provides for the carrier recovery functions.Note, this circuit is a typical Costas loop device for tracking thephase of a double-sided surpressed-carrier signal which is equivalent tothe squarer/Phase Lock Loop System of FIG. 7.

Referring now to FIG. 9, this drawing shows an embodiment of thedemodulation algorithm for demodulator 84 of FIG. 5A for demodulatingQPSK/QAM signals. It will be appreciated that this algorithm can bebroken down into elements or blocks which form demodulator 84 in FIG.5A. However, this algorithm can also be implemented in software suchthat the demodulator is software-configurable. Moreover, equalizer 86,Trellis decoder 88 and R-S decoder 90 can be implemented in software andappropriately configured. Note that an advantage of the softwareimplementation is flexibility.

As to further systems for setting modulation type or format, andreferring now to FIG. 10, it is possible to configure universalmodulator 40 utilizing a so-called "smart card" 120 and a card reader122. In this embodiment, the card has a priori knowledge of themodulator type or format expected and is used to set thesoftware-configurable logic in the modem. This eliminates the necessityof detecting modulation type or format while at the same time offering abilling function, since the use of the smart card and its embeddedinformation can be detected.

Referring now to FIG. 11, it is also possible to detect modulation typeor format through initially demodulating all modulation types, detectingthe error at MPU 124 and using a configuration database 126 to changethe software-configurable logic to that modulation type or format havingthe lowest error. Note that initial multiple modulation typedemodulation can be in parallel or serial.

Having now described a few embodiments of the invention, and somemodifications and variations thereto, it should be apparent to thoseskilled in the art that the foregoing is merely illustrative and notlimiting, having been presented by the way of example only. Numerousmodifications and other embodiments are within the scope of one ofordinary skill in the art and are contemplated as falling within thescope of the invention as limited only by the appended claims andequivalents thereto.

What is claimed is:
 1. A universal modem to accommodate differentmodulation formats for use in the modulation and demodulation of asignal, comprising:a modulator and demodulator havingsoftware-configurable logic means for providing modulation anddemodulation of a signal, said software configurable logic meansincluding functional hardware blocks, each performing a predeterminedfunction, and means for selectively interconnecting said hardwareblocks; means for generating, as an output, configuration instructionsfor said software-configurable logic means; and, means for coupling saidoutput to said software configurable logic means to configure said modemfor the modulation format specified by said configuration instructionsby interconnecting said hardware blocks to correspond to saidinstructions.
 2. A universal modem to accommodate different modulationformats for use in the modulation and demodulation of a signalcomprising:a modulator and demodulator, said demodulator havingsoftware-configurable logic means for providing demodulation of a signalhaving a predetermined modulation format, said software configurablelogic means including functional hardware blocks, each performing apredetermined function, and means for selectively interconnecting saidhardware blocks; means for ascertaining the modulation type of saidsignal and for generating, as an output, configuration instructions forsaid software-configurable logic means; and means for coupling saidoutput to said software configurable logic means, thereby to configuresaid demodulator for said modulation format by interconnecting saidhardware blocks to correspond to said instructions.
 3. The modem ofclaim 2, wherein said software-configurable logic means includes anumber of elements, each performing a different demodulation function,and means for interconnecting said elements to perform demodulation ofsaid signal in accordance with said configuration instructions.
 4. Themodem of claim 3, wherein said elements are taken from the groupconsisting of arithmetic logic units, registers, fifo buffers, gates,finite impulse response filters and infinite impulse response filters.5. The modem of claim 2, wherein said modulator includes saidsoftware-configurable logic means;software for configuring saidsoftware-configurable logic means to modulate a signal with apredetermined modulation format based on the configuration specified bysaid software; and, means for running said software to configure saidsoftware-configurable logic means.
 6. The modem of claim 2 wherein saiddemodulator includes a software-configurable equalizer and wherein saidcoupling means includes means for coupling said configurationinstructions to said equalizer.
 7. Apparatus to accommodate differentmodulation formats for use in the demodulation of a signal, comprising;ademodulator having software-configurable logic means for providingdemodulation of a signal having a predetermined modulation format, saidsoftware configurable logic means including functional hardware blocks,each performing a predetermined function, and means for selectivelyinterconnecting said hardware blocks; means for ascertaining themodulation format of said signal and for generating, as an output,configuration instructions for said software-configurable logic means;and, means for coupling said output to said software configurable logicmeans, thereby to configure said demodulator for said modulation formatby interconnecting said hardware blocks to correspond to saidinstructions.
 8. The apparatus of claim 7, wherein saidsoftware-configurable logic means includes a number of elements, eachperforming a different demodulation function, and means forinterconnecting said elements to perform demodulation of said signal inaccordance with said configuration instructions.
 9. The apparatus ofclaim 8, wherein said elements are taken from the group consisting ofarithmetic logic units, registers, fifo buffers, gates, finite impulseresponse filters and infinite impulse response filters.
 10. Apparatus toaccommodate different modulation formats for use in the modulation of asignal, comprising:a modulator having software-configurable logic meansfor providing a modulation format for said signal based on theconfiguration of said logic means, said software configurable logicmeans including functional hardware blocks, each performing apredetermined function, and means for selectively interconnecting saidhardware blocks; means for setting the modulation format for said signalby generating as an output configuration instructions for saidsoftware-configurable logic means; and, means for coupling said outputto said software configurable logic means, thereby to configure saidmodulator for the modulation format set by interconnecting said hardwareblocks to correspond to said instructions.
 11. The apparatus of claim10, wherein said software-configurable logic means includes a number ofelements, each performing a different modulation function, and means forinterconnecting said elements to perform modulation of said signal inaccordance with said configuration instructions.
 12. The apparatus ofclaim 11, wherein said elements are taken from the group consisting ofarithmetic logic units, registers, fifo buffers, gates, finite impulseresponse filters and infinite impulse response filters.
 13. In areceiving device adapted to receive signals of different modulationformats, a demodulator having a software-configurable logic unit, saidsoftware configurable logic unit including functional hardware blocks,each performing a predetermined function, and means for selectivelyinterconnecting said hardware blocks, said demodulator being coupled tothe output of said receiver; and a computer for configuring saidsoftware-configurable logic unit with configuration instructions suchthat said demodulator is set to demodulate a signal having apredetermined modulation format by interconnecting said hardware blocksto correspond to said instructions.
 14. The receiving device of claim 13wherein said receiving device has a channel selector and furtherincluding a channel detector having as an output the channel to whichsaid channel selector is set, means for coupling the output of saidchannel detector to said computer and means within said computer forsetting said predetermined modulation type to that expected for signalson the detected channel.
 15. The receiving device of claim 13 andfurther including a flag on the signal received at said receivingdevice, said flag indicating modulation format, a flag detector havingas an output the modulation format of said received signal, and meanswith said computer for setting said predetermined modulation type tothat indicated by the output of said flag detector.
 16. The receivingdevice of claim 13 and further including a smart card and a smart cardreader, said smart card having a code specifying the modulation formatof a signal to be received by said receiving device, said smart cardreader having an output coupled to said computer containing said codeand means within said computer for reading said code and setting saidpredetermined modulation type to that corresponding to said code.
 17. Ina receiving device adapted to receive signals of different modulationformats, a demodulator having a software-configurable logic unit, saiddemodulator being coupled to the output of said receiver; and a computerfor configuring said software-configurable logic unit such that saiddemodulator is set to demodulate a signal having a predeterminedmodulation format, said demodulator initially demodulating all expectedmodulation types and further including an error signal generator coupledto the output of said demodulator for generating an error signal, adetector for detecting for which modulation format said error signal isat a minimum after said demodulator demodulates all expected modulationformats and means within said computer for setting said predeterminedmodulation type to that modulation type having said minimum errorsignal.
 18. Apparatus to accommodate different modulation formats foruse in the demodulation of a signal received on an input, comprising:acontrol signal:a demodulator having software configurable logicincluding functional hardware blocks, each performing a predeterminedfunction, and selective interconnection of said hardware blocks, saiddemodulator employing different demodulator formats in terms of theinterconnection of said hardware blocks, said demodulator coupled tosaid input and providing demodulation of said signal having apredetermined format based on said control signal with said controlsignal specifying said interconnection: a detector coupled to said inputand generating as an output different instructions for differentdemodulation formats based on the detected demodulation format; and, amemory coupled between said demodulator and said detector for storingconfiguration data, said memory supplying said configuration data tosaid demodulator as said control signal to activate one of saiddifferent demodulation formats.